This paper introduces a tangible user interface (TUI) concept designed for child-oriented musical interaction and education by the name of COMB. The interaction concept of the interface is based upon the natural behavior and metaphors found in childrenâs play during construction with building-blocks. This paradigm is used to increase the accessibility of the otherwise expert-focused digital and electronic music to children. We evaluated our prototype during two different study setups. We found preliminary indications that this concept fosters imitation during learning. Therefore, the usage of shape as a meaningful element of interaction could be a promising design strategy for interfaces addressing children. In this paper we present the theoretical foundation of the concept as well as technical details of the prototype. Furthermore, we discuss how this concept can be applied to increase accessibility of technology in various other domains.